Anterior segment alterations in congenital primary aphakia-a clinicopathologic report of five cases

Congenital anterior segment ocular disorders: Genotype-phenotype correlations and emerging novel mechanisms

Development of the anterior segment of the eye requires reciprocal sequential interactions between the arising tissues, facilitated by numerous genetic factors. Disruption of any of these processes results in congenital anomalies in the affected tissue(s) leading to anterior segment disorders (ASD) including aniridia, Axenfeld-Rieger anomaly, congenital corneal opacities (Peters anomaly, cornea plana, congenital primary aphakia), and primary congenital glaucoma. Current understanding of the genetic factors involved in ASD remains incomplete, with approximately 50% overall receiving a genetic diagnosis. While some genes are strongly associated with a specific clinical diagnosis, the majority of known factors are linked with highly variable phenotypic presentations, with pathogenic variants in FOXC1, CYP1B1, and PITX2 associated with the broadest spectrum of ASD conditions. This review discusses typical clinical presentations including associated systemic features of various forms of ASD; the latest functional data and genotype-phenotype correlations related to 25 ASD factors including newly identified genes; promising novel candidates; and current and emerging treatments for these complex conditions. Recent developments of interest in the genetics of ASD include identification of phenotypic expansions for several factors, discovery of multiple modes of inheritance for some genes, and novel mechanisms including a growing number of non-coding variants and alleles affecting specific domains/residues and requiring further studies.

Secondary developmental glaucoma

The basic pathophysiology of all childhood glaucoma results from impaired outflow through the trabecular meshwork. Anterior Segment Dysgeneses (ASD) are a group of nonacquired anomalies associated with secondary developmental glaucoma, characterized by impaired development of the structures of the anterior segment. Many genes impact the development of the anterior segment. The cause of the development of the abnormalities is thought to be multifactorial. Molecular research has helped our understanding of the molecular basis of ASD and the developmental mechanisms underlying these conditions. Identifying the genetic changes underlying ASD has gradually led to the recognition that some of these conditions may be parts of a disease spectrum rather than isolated anomalies. The characterization of the underlying genetic abnormalities responsible for glaucoma is the first step toward developing diagnostic and screening tests, which could identify individuals at risk for disease before irreversible optic nerve damage occurs. It is also crucial for genetic counseling and risk stratification of later pregnancies. It also aids prenatal testing by various methods allowing for effective genetic counseling. This review summarizes various ocular and systemic conditions that result in secondary developmental glaucoma and provide an overview of the phenotypes, the diagnosis and principles of management of the various disorders.

Genetics of the anterior segment dysgenesis

The anterior segment dysgeneses are a broad group of heterogeneous disorders characterized by developmental abnormalities of the anterior segment of the eye, including primary congenital aphakia, Peters sequence, aniridia, and Axenfeld-Rieger spectrum. These conditions can have overlapping phenotypes and both genotypic and phenotypic heterogeneity. This article provides a strategy for both phenotyping and then genotyping using a targeted stepwise approach.

Variable phenotype of secondary congenital corneal opacities associated with microphthalmia with linear skin defects syndrome

To describe the anterior segment (AS) findings in patients with microphthalmia with linear skin defects syndrome (MLS), also known as microphthalmia, dermal aplasia, and sclerocornea (MIDAS). A retrospective chart review was conducted to identify patients with a diagnosis of MLS syndrome seen at UPMC Children's Hospital of Pittsburgh. Ophthalmic examination, high-frequency ultrasound, AS optical coherence tomography, and molecular testing were reviewed. Five female patients (10 eyes) were identified. One eye was anophthalmic, one was in a status post penetrating keratoplasty, and eight eyes presented with congenital corneal opacity (CCO). Of these, one showed a normal lens and a very small faint CCO; five showed congenital aphakia and characteristic silvery appearance of the cornea with vascularization; and two showed irido-corneal adhesions in association with normal or abnormal lens and localized avascular CCO. Genetic testing was performed and revealed involvement of HCCS in four patients. In MLS patients, kerato-irido-lenticular dysgenesis can be associated with secondary CCO. It is important to distinguish these CCO from sclerocornea, in order to refine the appropriate management and counseling the parents about the prognosis.

Primary aphakia: clinical recognition is the key to diagnosis

PURPOSE

To describe the presentation and treatment outcomes of a cohort of children with primary aphakia (PA).

METHODS

Clinical photographs and ultrasound biomicroscopy (UBM) images of children presenting with sclerocornea and undetermined anterior segment dysgenesis between July 2017 and December 2020 were reviewed retrospectively. Children who had no crystalline lens visible on UBM were included.

RESULTS

A total of 124 UBM images were captured for 124 children with cloudy corneas. Twelve children were identified with congenital primary aphakia: 5 had bilateral buphthalmos, 2 had buphthalmos in one eye and microphthalmos in the other, and 5 had bilateral sclerocornea-microphthalmia complex. All patients had a peculiar silvery-blue corneal appearance, with fine vascularization on the corneal surface. The overall corneal thickness was 409.1 ± 8.7 μm. The intraocular pressure (IOP) in eyes with glaucoma was 24.5 ± 7.3 mm Hg; in microphthalmic eyes, 11.4 ± 3.4 mm Hg (P <0.001). The raised IOP was treated with limited trans-scleral cyclophotocoagulation under transillumination and topical antiglaucoma medications. Children with glaucoma gained ambulatory vision with spectacles.

CONCLUSIONS

Congenital primary aphakia has a characteristic clinical appearance and may present as buphthalmos or microphthalmos, depending on the extent of dysgenesis. Incisional surgery may result in phthisis because of ciliary body dysgenesis and unpredictable aqueous production.

Update on Pediatric Corneal Diseases and Keratoplasty

Managing pediatric corneal disorders is challenging as the prognosis of pediatric keratoplasty depends on several factors. Advancements in the genetic basis of congenital corneal diseases and investigations in congenital corneal conditions provide a better understanding of pediatric corneal conditions. Surgeons performing keratoplasty in children now have a choice of various techniques. Evolving surgical techniques of anterior lamellar and endothelial keratoplasties has expanded the management interventions in these pediatric corneal morbidity conditions; however, considerable concerns still exist in association with corneal transplantation in infants and children. Outcomes in pediatric keratoplasty depend upon the preoperative indications, the timing of surgical intervention, intraoperative and postoperative factors including the patient/care givers' compliance. Factors such as low scleral rigidity, higher rate of graft failure, need for frequent examinations under anesthesia, and difficulty in optimal visual acuity assessment still remain a considerable challenge in pediatric scenarios. In children, deprivation amblyopia as a result of the corneal opacification can adversely affect visual development, causing dense amblyopia. Outcomes to surgical interventions for management of corneal opacification in children is further compromised by the pre-existing amblyopia apart from the concerns of refractive outcome of the graft. Graft rejection, graft infection, amblyopia, and glaucoma continue to be serious concerns. In recent years both anterior and posterior lamellar keratoplasty techniques are being increasingly performed in pediatric eyes, which offer advantages in the form of lower risk of graft rejection. The timing of surgery, careful case selection, cautious intraoperative approach, and optimal postoperative management can improve the anatomical and functional outcome in difficult cases.

Secondary developmental glaucoma in eyes with congenital aphakia

PURPOSE

To describe the clinical spectrum and management of glaucoma in congenital aphakia.

METHODS

The demographics and clinical spectrum of eyes with congenital aphakia with and without glaucoma were compared, and management outcomes of congenital aphakia cases with glaucoma were studied retrospectively between April 2000 and June 2020.

RESULTS

There were a total of 168 eyes (84 subjects) with a diagnosis of congenital aphakia, of which 29 eyes of 18 subjects were diagnosed with glaucoma. Corneal opacity was the presenting complaint in 26/29 eyes with glaucoma and 139/139 eyes without glaucoma. The (interquartile range (IQR)) horizontal corneal diameterwas 10.5mm (IQR, 9.0-12.5) and 8mm (IQR, 5-10) in eyes with and without glaucoma (P = 0.01), respectively. The median (IQR) axial length was 17.5mm (IQR, 13.5-19.5) and 15mm (IQR, 14-16) mm in eyes with and without glaucoma (P = 0.03), respectively. Nineteen eyes with glaucoma had adequate intraocular pressure (IOP) control with one medication. Three eyes underwent transscleral diode cyclophotocoagulation and maintained IOP without medications. Three eyes underwent trabeculectomy and trabeculotomy, trabeculectomy followed by penetrating keratoplasty, and trabeculectomy, respectively, of which two eyes became phthisical. At the last follow-up, the median (IQR) IOP was 14 mm Hg (IQR, 14-17) Hg. The median(IQR) follow-up duration was 4.53 months (IQR, 2.03- 48.06).

CONCLUSION

One-fifth of the eyes with congenital aphakia had secondary developmental glaucoma. The corneal diameter and axial lengths were higher in the eyes with glaucoma compared to eyes without glaucoma. Medical management is the preferred short-term mode of IOP control. Transscleral cyclophotocoagulation may be preferred over surgical intervention.

Comprehensive phenotypic and functional analysis of dominant and recessive FOXE3 alleles in ocular developmental disorders

The forkhead transcription factor FOXE3 is critical for vertebrate eye development. Recessive and dominant variants cause human ocular disease but the full range of phenotypes and mechanisms of action for the two classes of variants are unknown. We identified FOXE3 variants in individuals with congenital eye malformations and carried out in vitro functional analysis on selected alleles. Sixteen new recessive and dominant families, including six novel variants, were identified. Analysis of new and previously reported genetic and clinical data demonstrated a broad phenotypic range with an overlap between recessive and dominant disease. Most families with recessive alleles, composed of truncating and forkhead-domain missense variants, had severe corneal opacity (90%; sclerocornea in 47%), aphakia (83%) and microphthalmia (80%), but some had milder features including isolated cataract. The phenotype was most variable for recessive missense variants, suggesting that the functional consequences may be highly dependent on the type of amino acid substitution and its position. When assessed, aniridia or iris hypoplasia were noted in 89% and optic nerve anomalies in 60% of recessive cases, indicating that these defects are also common and may be underrecognized. In dominant pedigrees, caused by extension variants, normal eye size (96%), cataracts (99%) and variable anterior segment anomalies were seen in most, but some individuals had microphthalmia, aphakia or sclerocornea, more typical of recessive disease. Functional studies identified variable effects on the protein stability, DNA binding, nuclear localization and transcriptional activity for recessive FOXE3 variants, whereas dominant alleles showed severe impairment in all areas and dominant-negative characteristics.